Saw a sysadmin replace a dead hard drive without powering down the server and I called him reckless but that hot swap trick saved us 4 hours of downtime on a Friday.
My uncle Pete who ran IT for a school district told me hot swapping drives was asking for data corruption, but when we lost a drive mid-batch job last Tuesday, swapping it live kept everything running and the rebuild finished in 45 minutes without a single error, so has anyone else had that old school advice just not hold up under real pressure?